Francis-Type Pump for a Hydroelectric Power Plant

ABSTRACT

The invention relates to a Francis-type pump, comprising the following features:
         a blade wheel;   a spiral housing;       

     a suction pipe;
         a counter-swirl generator which is arranged in the inlet to the blade wheel and which can be activated during the start-up and deactivated after start-up, and which generates a swirl acting against the direction of rotation of the blade wheel.

The invention relates to a Francis-type pump for a hydroelectric power plant for pumping water from a downstream reservoir to an upstream reservoir.

Such a pump comprises a blade wheel, a spiral housing and a suction pipe.

It can be a component of a pump-storage power station. It can be operated as a turbine when the water flows from the upstream reservoir to the downstream reservoir (see WO 2010/094887 A1).

Such a pump is designed to meet certain parameters that are based on the power station, especially a specific pumping head and a specific throughput.

Problems frequently occur in such pumps during the start-up. The problems are that conveyance of water does not occur during start-up because the flow is unstable.

The inventors have recognized the following:

The problems occur when the pumping head exceeds a magnitude on which the construction is based. This may occur for example when the upstream water level is especially high or the downstream water level is especially low, or if both occur simultaneously. They have therefore recognized the pumping head as an especially critical quantity.

The invention is based on the object of providing a pump of the kind mentioned above in such a way that the flow is also stable in the case of high pumping heads and the start-up of the pump will be enabled.

The solution consists of the following:

-   -   Swirl generators are provided in the inlet to the pump.     -   A number of guide elements are associated with the suction pipe         which are arranged on the circumference of the suction pipe and         which can be moved into the flow guided by the suction tube         during the start-up of the pump.     -   The guide elements are configured and arranged in such a way         that they provide a swirl to the flow which is opposite of the         rotation of the blade wheel. This allows stabilizing the flow         during start-up.

The guide elements can be moved back again once a stable flow has been produced by the counter-swirl during start-up.

The invention and the state of the art are explained below in closer detail by reference to the drawings, which show the following in detail:

FIG. 1 shows a Francis-type pump as a component of a hydroelectric power plant in a vertical sectional view;

FIG. 2 shows a schematic axially sectional view of the part of the suction pipe adjacent to the blade wheel;

FIG. 3 shows the subject matter of FIG. 2 in a view along III-III;

FIG. 4 schematically shows an axially vertical sectional view through the suction pipe with a plurality of hydraulic swirl generators.

FIG. 5 shows a suction pipe according to the state of the art with streamlines.

The Francis-type pump as shown in FIG. 1 comprises a blade wheel 1 which is enclosed by a spiral housing 2.

A suction pipe 3 is arranged upstream of the blade wheel 1. The volume flow produced by the blade wheel 1 will be supplied from the spiral housing to an ascending pipe 4.

The end of the suction pipe on the inlet side immerses into a downstream reservoir (not shown). The end of the ascending pipe on the outlet side opens into an upstream reservoir (not shown).

The pump is driven by an electric motor 5. The blade wheel 1 and the electric motor 5 are arranged coaxially and are in drive connection with each other via a shaft 6.

The suction pipe 3 comprises an inlet section 3.1, an elbow 3.2 and an outlet section 3.3 provided upstream of the blade wheel 1.

The relevant component is a device for producing a swirl in opposite direction to the blade wheel 1. This device comprises a plurality of counter-swirl generators 7. They are arranged on the outlet section 3.3 of the suction pipe (see FIGS. 2 and 3).

The counter-swirl generator 7 as shown in FIG. 2 is arranged as follows:

The wall of the outlet section 3.3 comprises a pocket 3.4 in its region close to the blade wheel. A guide element 7.1 is displaceable by means of an adjusting device 3.5 with more or less distance from the rotational axis 1.1 of the blade wheel 1. The guide element can be arranged in the shape of a blade.

FIG. 3 shows that the guide element 7.1 is inclined against the plane of the rotational axis 1.1. This is the precondition that a swirl will be produced in the flow in the outlet section 3.3.

It is also possible to adjustably mount the guide element 7.1, so that the inclination against the plane of the rotational axis 1.1 and therefore also the swirl will be changed. Several counter-swirl generators 7 are provided, e.g. 2, 3, 4. It is also possible to provide only one single counter-swirl generator 7.

The counter-swirl generator can also have a shape that differs from the one that is shown. Consequently, the guide element can also be arranged as a rotatable element, comprising a rotational axis and a plurality of blades disposed on the rotational axis. A non-mechanical solution can also be considered. Nozzles can be provided for example with which the suction pipe is equipped, e.g. in its outlet section 3.3. The nozzles can be connected to a flowable medium (generally water) and are directed in such a way that the desired counter-swirl is produced in the flow in the suction tube 3.

FIG. 4 schematically illustrates a hydraulic solution. Several swirl-generating nozzles 8 are arranged in the wall of suction pipe 3. Water jets are introduced here. The direction of the jets is illustrated by the arrows.

FIG. 5 schematically shows a suction pipe 3 of a hydraulic pump with a streamline diagram. The suction pipe is not provided with the counter-swirl generators in accordance with the invention. The illustration shows that separations X occur on the inner wall regions of the curvature of the suction pipe.

The invention can also be applied to pump turbines. The counter-swirl generators will be activated in pumping operation in such a case, which again only occurs during start-up.

LIST OF REFERENCE NUMERALS

1 Blade wheel

1.1 Rotational axis

2 Spiral housing

3 Suction pipe

3.1 Inlet section

3.2 Elbow

3.3 Outlet section

3.4 Pocket

3.5 Adjusting device

4 Ascending pipe

5 Electric motor

6 Shaft

7 Counter-swirl generator

7.1 Guide element

8 Swirl generating nozzles 

1-6. (canceled)
 7. A Francis-type pump comprising: a blade wheel; a spiral housing; a suction pipe; a counter-swirl generator which is arranged in the inlet to the blade wheel and which can be activated during the start-up in the pumping direction, and which can be deactivated after start-up, and which generates a swirl acting against the direction of rotation of the blade wheel.
 8. The Francis-type pump according to claim 7, wherein the counter-swirl generator is a component of a pump turbine.
 9. The Francis-type pump according to claim 7, wherein the counter-swirl generator comprises guide elements.
 10. The Francis-type pump according to claim 8, wherein the counter-swirl generator comprises guide elements.
 11. The Francis-type pump according to claim 7, wherein the counter-swirl generator comprises a plurality of swirl-generating nozzles.
 12. The Francis-type pump according to claim 8, wherein the counter-swirl generator comprises a plurality of swirl-generating nozzles.
 13. The Francis-type pump according to claim 7, wherein the counter-swirl generator is arranged in the outlet section of the suction pipe.
 14. The Francis-type pump according to claim 8, wherein the counter-swirl generator is arranged in the outlet section of the suction pipe.
 15. The Francis-type pump according to claim 9, wherein the counter-swirl generator is arranged in the outlet section of the suction pipe.
 16. The Francis-type pump according to claim 10, wherein the counter-swirl generator is arranged in the outlet section of the suction pipe.
 17. The Francis-type pump according to claim 11, wherein the counter-swirl generator is arranged in the outlet section of the suction pipe.
 18. The Francis-type pump according to claim 12, wherein the counter-swirl generator is arranged in the outlet section of the suction pipe.
 19. The Francis-type pump according to claim 7, wherein the counter-swirl generator comprises a plurality of units which are grouped around the rotational axis.
 20. The Francis-type pump according to claim 8, wherein the counter-swirl generator comprises a plurality of units which are grouped around the rotational axis.
 21. The Francis-type pump according to claim 9, wherein the counter-swirl generator comprises a plurality of units which are grouped around the rotational axis.
 22. The Francis-type pump according to claim 10, wherein the counter-swirl generator comprises a plurality of units which are grouped around the rotational axis.
 23. The Francis-type pump according to claim 11, wherein the counter-swirl generator comprises a plurality of units which are grouped around the rotational axis.
 24. The Francis-type pump according to claim 12, wherein the counter-swirl generator comprises a plurality of units which are grouped around the rotational axis.
 25. The Francis-type pump according to claim 13, wherein the counter-swirl generator comprises a plurality of units which are grouped around the rotational axis.
 26. The Francis-type pump according to claim 14, wherein the counter-swirl generator comprises a plurality of units which are grouped around the rotational axis. 